Fiber and fiber production method

Abstract

To provide a fiber that contains ultra-high molecular weight polyethylene and polyethylene having a lower intrinsic viscosity [η] than that of the ultra-high molecular weight polyethylene, and has excellent tensile strength and stretching property, and also a production method in which fibers are produced without using a solvent.SOLUTION: A fiber (Y) comprises 5 to 40 pts.mass of an ultra-high molecular weight polyethylene (A) satisfying a requirement (a-1) and 95 to 60 pts.mass of a low-molecular weight or high-molecular weight polyethylene (B) satisfying requirements (b-1) and (b-2) and has an intrinsic viscosity [η] measured in decalin solvent at 135°C in a range of 1.5 to 15 dL / g, and at least a portion thereof forme a homogeneous phase. Requirement (a-1): an intrinsic viscosity [η] measured in decalin at 135°C is 8 to 50 dL / g. Requirement (b-1): an intrinsic viscosity [η] measured in decalin at 135°C is 0.1 to 5 dL / g. Requirement (b-2): a density is 950 to 985 kg / m3.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to fibers and methods for making fibers. [Background technology]

[0002] Compared to general-purpose resins such as ordinary polyethylene, ultra-high molecular weight polyethylene has weaker intermolecular cohesion, a symmetrical molecular structure, and a high degree of crystallinity, which gives it excellent sliding properties, as well as excellent impact resistance, abrasion resistance, tensile strength, etc., making it suitable for a variety of applications. However, because ultra-high molecular weight polyethylene is difficult to mold due to its high molecular weight, it is often difficult to directly use the methods used to mold general-purpose polyethylene.

[0003] Therefore, various methods have been proposed to improve the moldability of ultra-high molecular weight polyethylene without impairing its excellent properties, such as blending ultra-high molecular weight polyethylene with polyethylene having a low intrinsic viscosity [η].

[0004] For example, Patent Document 1 discloses a polyolefin composition for injection molding, which is composed of 15 to 40% by weight of an ultra-high molecular weight polyolefin having an intrinsic viscosity [η] of 10 to 40 dL / g and 85 to 60% by weight of a low- to high-molecular weight polyolefin having an intrinsic viscosity [η] of 0.1 to 5 dL / g. This composition has the advantage that it can be injection molded despite containing an ultra-high molecular weight polyolefin, and furthermore, molded articles obtained by injection molding are excellent in that they retain the excellent sliding properties and wear resistance of the ultra-high molecular weight polyolefin.

[0005] Patent Document 2 discloses a composition obtained by blending a polyethylene resin composition containing more than 35% by weight but not more than 90% by weight of ultra-high molecular weight polyethylene having an intrinsic viscosity [η] of 10 to 40 dL / g and 10% by weight or more but less than 65% by weight of low-molecular-weight or high-molecular-weight polyethylene having an intrinsic viscosity [η] of 0.1 to 5 dL / g with a specific polyolefin resin composition. This composition produces molded articles with an excellent balance of abrasion resistance, appearance, and moldability.

[0006] On the other hand, to obtain fibers from general-purpose resins including ultra-high molecular weight polyethylene, a gel spinning method is sometimes used in which the resin is dissolved in a solvent and spun into a gel. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Unexamined Patent Publication No. 63-12606 [Patent Document 2] International Publication No. 2003 / 022920 Summary of the Invention [Problem to be solved by the invention]

[0008] As proposed in Patent Documents 1 and 2, when fibers are produced from a resin obtained by blending ultra-high molecular weight polyethylene with polyethylene having a low intrinsic viscosity [η], it is possible to produce fibers by melt spinning in the same way as with general-purpose polyethylene, but the tensile strength and drawability of the obtained fibers are insufficient depending on the application. Furthermore, the gel spinning method uses a solvent and includes a step of removing the solvent, which raises concerns about its impact on the human body and the environment, and also leads to problems such as a complicated production process and high production costs.

[0009] The present invention aims to provide a fiber that contains ultra-high molecular weight polyethylene and polyethylene having a lower intrinsic viscosity [η] than the ultra-high molecular weight polyethylene, and that has excellent tensile strength and stretchability, and to produce the fiber without using a solvent. [Means for solving the problem]

[0010] As a result of further research, the present inventors have found that the above-mentioned problems can be solved by the following configuration example. In this specification, the numerical range "A to B" indicates A or more and B or less.

[0011] [1] A composition comprising 5 to 40 parts by mass of an ultra-high molecular weight polyethylene (A) that satisfies the following requirement (a-1) and 95 to 60 parts by mass of a low-molecular weight or high-molecular weight polyethylene (B) that satisfies the following requirements (b-1) and (b-2) (the total amount of polyethylene (A) and polyethylene (B) being 100 parts by mass), Fiber (Y) having an intrinsic viscosity [η] measured in decalin solvent at 135 ° C. in the range of 1.5 to 15 dl / g and at least a part of which forms a homogeneous phase: (a-1) The intrinsic viscosity [η] measured in decalin solvent at 135°C is 8 to 50 dl / g; (b-1) The intrinsic viscosity [η] measured in decalin solvent at 135°C is 0.1 to 5 dl / g; (b-2) Density is 950 to 985 kg / m 3 is.

[0012] [2] The fiber (Y) according to [1], wherein the homogeneous phase is a phase in which no domains of 3 μm or more are observed when the cross section of the fiber is observed under a laser microscope at a magnification of 1000 times.

[0013] [3] The fiber (Y) according to [1] or [2], having a fiber diameter of 200 denier or less.

[0014] [4] The fiber (Y) according to any one of [1] to [3], which has a draw ratio of 25 times or more.

[0015] [5] The intrinsic viscosity [η] measured in decalin solvent at 135°C is 0.1 to 5 dl / g, and the density is 950 to 985 kg / m 3 a first step of producing a low-molecular-weight to high-molecular-weight polyethylene (B), a second step of producing, after the first step, an ultra-high molecular weight polyethylene (A) having an intrinsic viscosity [η] measured in a decalin solvent at 135°C in the range of 8 to 50 dl / g; by a multi-stage polymerization method including at least two steps of a step of producing a polyethylene resin composition (X) having an intrinsic viscosity [η] measured in a decalin solvent at 135°C in the range of 1.5 to 15 dl / g and at least a part of which forms a homogeneous phase; a spinning step of spinning the polyethylene resin composition (X); A method for producing a fiber (Y), comprising: [Effects of the Invention]

[0016] The present invention provides a fiber containing ultra-high molecular weight polyethylene and polyethylene having a lower intrinsic viscosity [η] than that of the ultra-high molecular weight polyethylene, and having excellent tensile strength and extensibility. Furthermore, the fiber can be produced without using a solvent. DETAILED DESCRIPTION OF THE INVENTION

[0017] Fiber (Y) The fiber (Y) according to the present invention contains a specific ultra-high molecular weight polyethylene (A) and a specific low- to high-molecular weight polyethylene (B) (hereinafter also referred to as "polyethylene (B)") and satisfies the following requirements (x-1) and (x-2). In the following description, the resin composition that is the material for the fiber (Y) will also be referred to as a polyethylene resin composition (X) (or "resin composition (X)"). In other words, the fiber (Y) is a fiber obtained by spinning the resin composition (X).

[0018] [Requirements (x-1)] The intrinsic viscosity [η] of the fiber (Y) as a sample measured in decalin solvent at 135°C is in the range of 1.5 to 15 dL / g, preferably in the range of 1.5 to 10 dL / g, more preferably in the range of 2.0 to 8.0 dL / g, and even more preferably in the range of 2.0 to 7.0 dL / g. That is, the intrinsic viscosity [η] of the resin composition (X) measured in decalin solvent at 135°C satisfies the above range. When the intrinsic viscosity [η] of the resin composition (X) in decalin solvent at 135°C satisfies the above range, the resin composition (X) has high melt fluidity that facilitates melt spinning and high abrasion resistance, thereby achieving both abrasion resistance and moldability. As a result, the fiber (Y) obtained from the resin composition (X) also has high abrasion resistance. If the intrinsic viscosity [η] in decalin solvent at 135°C is less than 1.5 dL / g, the abrasion resistance of the composition is impaired, and the abrasion resistance of the fibers obtained from such a composition tends to be poor. On the other hand, if the intrinsic viscosity [η] in decalin solvent at 135°C is more than 15 dL / g, the fluidity of the composition decreases, and the moldability tends to be impaired.

[0019] [Requirements (x-2)] At least a portion of the fiber (Y) forms a homogeneous phase. That is, in at least a portion of the fiber (Y), the ultra-high molecular weight polyethylene (A) and the polyethylene (B) are compatible with each other to form a homogeneous phase, and in the homogeneous phase portion, phase separation between the ultra-high molecular weight polyethylene (A) and the polyethylene (B) does not occur.

[0020] Whether at least a part of the fiber (Y) is a homogeneous phase or not is judged as follows based on the size of the island phases (domains) observed when a thin section prepared by cutting the fiber (Y) perpendicular to the longitudinal direction (stretching direction) with a microtome (i.e., cutting in the cross-sectional direction of the fiber (Y)) is observed with a laser microscope. The observation conditions with the laser microscope are as described in the examples below. Homogeneous phase: The cross section of the fiber (Y) does not contain domains of 3 μm or more. Phase separation: The cross section of the fiber (Y) contains domains of 3 μm or more. That is, it is preferable that the fibers (Y) do not have an island-sea structure containing domains of 3 μm or more in at least a part thereof.

[0021] Fibers (Y) in which ultra-high molecular weight polyethylene (A) and polyethylene (B) are compatible with each other to form a homogeneous phase at least in part are preferred because they have excellent abrasion resistance, tensile strength, and sliding properties, as well as excellent surface smoothness. One reason why fiber (Y) has excellent abrasion resistance, tensile strength, and sliding properties is presumably because the abrasion resistance, tensile strength, and sliding properties inherent in ultra-high molecular weight polyethylene (A) are particularly strong in areas where ultra-high molecular weight polyethylene (A) and polyethylene (B) are compatible enough to form a homogeneous phase. Fiber (Y) exhibits particularly good abrasion resistance when areas in which ultra-high molecular weight polyethylene (A) and polyethylene (B) form a homogeneous phase are distributed throughout fiber (Y), or when the entire fiber (Y) forms a homogeneous phase. Fiber (Y) has excellent surface smoothness because at least a portion of fiber (Y) does not contain domains of 3 μm or more, which reduces the occurrence of roughness due to domains located on the surface of fiber (Y).

[0022] When the ultra-high molecular weight polyethylene (A) and the polyethylene (B) are phase-separated, an island-sea structure is formed in which the ultra-high molecular weight polyethylene (A) forms domains (island phases) and the polyethylene (B) forms the matrix (sea phase). In this case, the abrasion resistance and sliding properties inherent in the ultra-high molecular weight polyethylene (A) are not exhibited throughout the fiber, so the polyethylene (B) wears, and then the domains located on the abrasion surface fall off, further increasing the abrasion resistance of the fiber, which tends to impair the abrasion resistance of the fiber. Furthermore, fibers in which an island-sea structure is formed tend to exhibit less tensile strength than fibers in which an island-sea structure is not formed. Furthermore, when fibers are spun from a composition in which the ultra-high molecular weight polyethylene (A) and the polyethylene (B) are phase-separated, the domains formed by the ultra-high molecular weight polyethylene (A) are located near the surface of the fiber, which tends to cause roughness and impair the surface smoothness of the fiber.

[0023] <Resin composition (X)> Resin composition (X) contains ultra-high molecular weight polyethylene (A) and polyethylene (B) and satisfies the requirements (x-1) and (x-2). That is, the intrinsic viscosity [η] of resin composition (X) measured in decalin solvent at 135°C satisfies the range described in relation to requirement (x-1). Furthermore, at least a portion of resin composition (X) forms a homogeneous phase.

[0024] The content of the ultra-high molecular weight polyethylene (A) in the resin composition (X) is 5 to 40 parts by mass, preferably 8 to 30 parts by mass, more preferably 10 to 25 parts by mass, and even more preferably 12 to 20 parts by mass (where the total amount of the ultra-high molecular weight polyethylene (A) and the polyethylene (B) is 100 parts by mass). The content of polyethylene (B) in resin composition (X) is 60 to 95 parts by mass, preferably 70 to 92 parts by mass, more preferably 75 to 90 parts by mass, and even more preferably 80 to 88 parts by mass (where the total amount of ultra-high molecular weight polyethylene (A) and polyethylene (B) is 100 parts by mass). When the contents of the ultra-high molecular weight polyethylene (A) and the polyethylene (B) are within the above ranges, the resin composition (X) can be easily melt-spun and has good abrasion resistance.

[0025] If the content of ultra-high molecular weight polyethylene (A) in the composition exceeds 40 parts by mass and the content of polyethylene (B) is less than 60 parts by mass, the melt fluidity of the composition will be low, making it difficult to melt spin the composition. On the other hand, if the content of ultra-high molecular weight polyethylene (A) is less than 5 parts by mass and the content of polyethylene (B) is more than 95 parts by mass, the abrasion resistance derived from the ultra-high molecular weight polyethylene (A) will be insufficient, and the abrasion resistance of the resulting composition will tend to be poor.

[0026] It is speculated that not only the contents of ultra-high molecular weight polyethylene (A) and polyethylene (B) but also the fact that at least a portion of resin composition (X) forms a homogeneous phase are related to the ease of melt spinning and abrasion resistance of resin composition (X). That is, it is speculated that in the portion where ultra-high molecular weight polyethylene (A) and polyethylene (B) form a homogeneous phase, viscosity unevenness is less likely to occur during melt spinning than when ultra-high molecular weight polyethylene (A) and polyethylene (B) are phase-separated. As a result, it is speculated that in the portion where ultra-high molecular weight polyethylene (A) and polyethylene (B) form a homogeneous phase, viscosity unevenness is less, resulting in a stable fiber diameter and less fiber breakage. That is, it is speculated that stress concentration at the thin portion of the fiber caused by viscosity unevenness, which causes breakage, is less likely to occur. Thus, because there are homogeneous phase portions in which breakage due to viscosity unevenness is unlikely to occur, resin composition (X) can be easily melt-spun, even though it is a resin containing a relatively large amount of ultra-high molecular weight polyethylene (A). Furthermore, melt spinning does not require dissolving resin composition (X) in a solvent, so fibers can be produced without using a solvent.

[0027] <Ultra-high molecular weight polyethylene (A)> The ultra-high molecular weight polyethylene (A) blended into the resin composition (X) has an intrinsic viscosity [η] measured in decalin solvent at 135° C. of 8 to 50 dL / g, preferably 8 to 45 dL / g, more preferably 8.5 to 45 dL / g, even more preferably 9 to 42 dL / g, and particularly preferably 9.5 to 42 dL / g. When the intrinsic viscosity [η] of the ultra-high molecular weight polyethylene (A) is within the above range, the resin composition (X) not only has excellent abrasion resistance, tensile strength, and sliding properties, but also has excellent moldability to the extent that melt spinning is easy, and as a result, a fiber (Y) having excellent abrasion resistance, tensile strength, and sliding properties can be obtained.

[0028] When an ultra-high molecular weight polyethylene having an intrinsic viscosity [η] of less than 8 dL / g measured in decalin solvent at 135°C is used instead of the ultra-high molecular weight polyethylene (A), the abrasion resistance of the composition deteriorates, and the abrasion resistance of the resulting molded article tends to be inferior.On the other hand, when an ultra-high molecular weight polyethylene having an intrinsic viscosity [η] of more than 50 dL / g measured in decalin solvent at 135°C is used instead of the ultra-high molecular weight polyethylene (A), the melt fluidity of the composition decreases, and therefore breakage tends to occur easily during stretching.

[0029] The ultra-high molecular weight polyethylene (A) is an ethylene homopolymer or a copolymer of ethylene and an α-olefin such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, or 3-methyl-1-pentene. The ultra-high molecular weight polyethylene (A) is preferably an ethylene homopolymer or a copolymer of ethylene and the above α-olefin, a copolymer composed mainly of ethylene, and more preferably an ethylene homopolymer. Here, the term "main component" refers to the component with the highest content (mol %) of the structural units contained in the polymer.

[0030] <Low-molecular-weight or high-molecular-weight polyethylene (B)> The polyethylene (B) has an intrinsic viscosity [η] of 0.1 to 5 dL / g, preferably 0.5 to 2 dL / g, more preferably 0.7 to 1.5 dL / g, and even more preferably 0.8 to 1.2 dL / g, measured in decalin at 135°C. When the polyethylene (B) has an intrinsic viscosity [η] within the above range, a resin composition (X) is obtained that is excellent in abrasion resistance, tensile strength, and sliding properties, and also has such excellent moldability that melt spinning is easy, and as a result, a fiber (Y) is obtained that is excellent in abrasion resistance, tensile strength, and sliding properties.

[0031] When a low-molecular-weight or high-molecular-weight polyethylene having an intrinsic viscosity [η] of less than 0.1 dL / g measured in decalin at 135°C is used instead of polyethylene (B), the abrasion resistance of the composition tends to deteriorate, and the abrasion resistance of the resulting fiber tends to be poor. On the other hand, when a low-molecular-weight or high-molecular-weight polyethylene having an intrinsic viscosity [η] of more than 5 dL / g measured in decalin at 135°C is used instead of polyethylene (B), the melt fluidity of the composition tends to decrease, resulting in a decrease in the moldability of the composition and a tendency for melt spinning to become difficult.

[0032] Polyethylene (B) has a density of 950 to 985 kg / m 3 and preferably 960 to 980 kg / m 3 and more preferably 960 to 975 kg / m 3 and more preferably 965 to 975 kg / m 3 When the density of the polyethylene (B) is within the above range, a resin composition (X) excellent in both abrasion resistance and moldability can be obtained.

[0033] Instead of polyethylene (B), the density is 950 kg / m 3 When a low-molecular-weight or high-molecular-weight polyethylene having a density of less than 985 kg / m is used, the low-molecular-weight or high-molecular-weight polyethylene has a low crystallinity and is easily scraped, and as a result, the abrasion resistance of the composition tends to deteriorate, and the abrasion resistance of the obtained fiber tends to be poor. 3 Therefore, the resin composition (X) has a viscosity of 985 kg / m 3 Low to high molecular weight polyethylenes of the following densities are used:

[0034] The polyethylene (B) is an ethylene homopolymer or a copolymer of ethylene and an α-olefin, preferably an ethylene homopolymer. The α-olefin constituting the copolymer includes linear or branched α-olefins having 3 to 20 carbon atoms, specifically propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 3,4-dimethyl-1-pentene, 4-methyl-1-hexene, 3-ethyl-1-pentene, 3-ethyl-4-methyl-1-pentene, 3,4-dimethyl-1-hexene, 4-methyl-1-heptene, 3,4-dimethyl-1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, etc. Among these, propylene and 1-butene are preferably used in view of the density range of the polyethylene (B).

[0035] In addition, the copolymer of ethylene and an α-olefin preferably contains 90 mol % or more of structural units derived from ethylene, and more preferably 95 mol % or more of structural units derived from ethylene. When the polyethylene (B) is a copolymer of ethylene and an α-olefin, the greater the amount of structural units derived from ethylene, the better.

[0036] <Other ingredients> The resin composition (X) and the fiber (Y) obtained from the resin composition (X) may contain other thermoplastic resins such as polyolefin resins (provided that they are different from the ultra-high molecular weight polyethylene (A) and the polyethylene (B)), and resin additives (for example, stabilizers such as heat stabilizers and weather stabilizers, crosslinking agents, crosslinking aids, antistatic agents, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, pigments, fillers, mineral oil-based softeners, petroleum resins, waxes, etc.), as long as the object of the present invention is not impaired. When the other components are contained, the total amount of the other components in the resin composition (X) (or in the fiber (Y) obtained from the resin composition (X)) is usually 5% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less. In other words, the proportion of the sum of the mass of the ultra-high molecular weight polyethylene (A) and the mass of the polyethylene (B) in the resin composition (X) to the mass of the resin composition (X) is usually 95% by mass or more, preferably 98% by mass or more, and more preferably 99% by mass or more. Similarly, the proportion of the sum of the mass of the ultra-high molecular weight polyethylene (A) and the mass of the polyethylene (B) in the fiber (Y) to the mass of the fiber (Y) is usually 95% by mass or more, preferably 98% by mass or more, and more preferably 99% by mass or more.

[0037] <Method for producing polyethylene resin composition (X)> Hereinafter, a method for producing the resin composition (X) will be described, but the treatment carried out in the method for producing the resin composition (X) is also a production step in the method for producing the fiber (Y) described below. Resin composition (X) is produced by a multi-stage polymerization method comprising at least two steps: a first step of producing polyethylene (B) in the presence of a known olefin polymerization catalyst; and a second step of producing ultra-high molecular weight polyethylene (A). The second step is carried out in the presence of the polyethylene (B) produced in the first step.

[0038] It is presumed that when ultra-high molecular weight polyethylene (A) is produced in the presence of polyethylene (B), a granular polyethylene resin composition is obtained in which particles of ultra-high molecular weight polyethylene (A) are coated with polyethylene (B). It is presumed that when the particle surfaces of the polyethylene resin composition are coated with polyethylene (B), the polyethylene resin composition is less likely to form an islands-in-sea structure and more likely to form a homogeneous phase when it is molded, for example, by melt-spinning into a fiber.

[0039] On the other hand, even when a multi-stage polymerization method is used, if ultra-high molecular weight polyethylene (A) is produced before polyethylene (B) and polyethylene (B) is produced in the presence of ultra-high molecular weight polyethylene (A), the resulting composition does not form a homogeneous phase. This is presumably because, in the composition obtained when polyethylene (B) is produced in the presence of ultra-high molecular weight polyethylene (A), polyethylene (B) is coated with ultra-high molecular weight polyethylene (A), and when the polyethylene resin composition is molded into fibers or the like, it is likely to form a sea-island structure and it is difficult to form a homogeneous phase.

[0040] When producing the resin composition (X), the olefin such as ethylene used in the polymerization can be any of the various olefins described in the sections on the ultra-high molecular weight polyethylene (A) and polyethylene (B) without any restrictions.

[0041] <Method for manufacturing fiber (Y)> The method for producing the fiber (Y) includes a producing step of producing the resin composition (X) and a spinning step of spinning the resin composition (X). The producing step of producing the resin composition (X) is as described in the method for producing the resin composition (X).

[0042] [Spinning process] The fiber (Y) can be obtained, for example, by extruding the molten resin composition (X) through a spinneret. By this method, for example, monofilaments, multifilaments, flat yarns, cut fibers, and nonwoven fabrics can be produced.

[0043] The melting temperature in the melt spinning process for producing monofilaments, multifilaments, and flat yarns can be selected appropriately depending on the melting points of the ultra-high molecular weight polyethylene (A) and polyethylene (B) contained in the resin composition (X), but is preferably in the range of 180 to 300° C., more preferably 200 to 270° C. When the melting temperature is within the above range, excessive thermal decomposition of the ultra-high molecular weight polyethylene (A) and polyethylene (B) can be suppressed, and the elongational viscosity of the fibrous strand extruded from the spinneret can be sufficiently reduced, resulting in fibers that have excellent mechanical strength and good spinnability.

[0044] The fibers thus obtained may be further drawn. The degree of drawing can be, for example, to such an extent that the ultra-high molecular weight polyethylene (A) and the polyethylene (B) are effectively oriented in at least one direction, thereby improving the modulus of elasticity and strength. The draw ratio is preferably 25 times or more, more preferably 25 to 80 times, and even more preferably 40 to 60 times.

[0045] The drawing temperature when carrying out the above drawing operation can be appropriately selected depending on the glass transition temperature and melting point of the ultra-high molecular weight polyethylene (A) and the polyethylene (B) or the strength and elongation of the fiber obtained after drawing, but is preferably 100 to 150° C., more preferably in the range of 120 to 145° C. When the drawing temperature is within the above range, yarn breakage is suppressed and fibers can be obtained stably.

[0046] When the above-mentioned stretching operation is carried out, it may be a one-stage stretching method or a multi-stage stretching method of two or more stages.

[0047] The cross-sectional shape of the fibers (Y) is not particularly limited, and may be a perfect circle or a non-circular, so-called irregular cross section. Examples of irregular cross sections include polygonal, elliptical, flat, multi-lobed shapes having many branches on the fiber surface (specifically, multi-lobed shapes with 3 to 32 lobes), star, C-shaped, H-shaped, S-shaped, T-shaped, Y-shaped, and W-shaped shapes.

[0048] Furthermore, the fiber (Y) may be a solid fiber that does not have a continuous cavity portion in the longitudinal direction of the fiber cross section.

[0049] <Physical properties of fiber (Y)> Fiber (Y) is obtained by spinning resin composition (X), and therefore contains all components contained in resin composition (X), and the amount of each component is the same as the amount in resin composition (X). For example, the content of the ultra-high molecular weight polyethylene (A) in the fiber (Y) is 5 to 40 parts by mass, preferably 8 to 30 parts by mass, more preferably 10 to 25 parts by mass, and even more preferably 12 to 20 parts by mass (where the total amount of the ultra-high molecular weight polyethylene (A) and the polyethylene (B) is 100 parts by mass). Similarly, the content of polyethylene (B) in fiber (Y) is 60 to 95 parts by mass, preferably 70 to 92 parts by mass, more preferably 75 to 90 parts by mass, and even more preferably 80 to 88 parts by mass (where the total amount of ultra-high molecular weight polyethylene (A) and polyethylene (B) is 100 parts by mass).

[0050] The fiber diameter of the fiber (Y) is preferably 200 denier or less, more preferably 70 to 150 denier, and even more preferably 80 to 140. The fiber diameter of the fiber (Y) is measured by the method described in the Examples.

[0051] The tensile strength of the fiber (Y) (tensile strength when the fiber (Y) is in a dry, unwet state) is preferably 6.0 gf / D or more, more preferably 6.3 gf / D or more, and more preferably 6.5 gf / D or more. The upper limit of the tensile strength of the fiber (Y) is not particularly limited, but is usually 8.0 gf / D. When the tensile strength of the fiber (Y) is in the above range, the fiber (Y) has excellent sliding properties and abrasion resistance. The tensile strength of the fiber (Y) is determined by the method described in the Examples.

[0052] <Uses of Fiber (Y)> The fiber (Y) can be widely used for conventionally known polyethylene applications, but since it is particularly excellent in abrasion resistance and tensile strength, applications requiring these include the following: For example, by forming it into the form of monofilament, multifilament, or flat yarn, it can be used in ropes, protective nets, fishing nets, fishing lines, life jackets, dental floss, toothbrushes, brushes, wigs, bags, shoes, curtains, carpets, car mats, insect screens, women's clothing, men's clothing, linings, underwear, down, vests, windbreakers, socks, shoe insoles, masks, surgical gowns, release cloths, oil-absorbent cloths, waterproof cloths, outdoor wear, supports, bandages, sleeping bag fabrics, tent fabrics, skis, etc. The fiber (Y) is suitable for applications such as sportswear such as apparel, golf wear, and swimsuits, artificial turf, futon batting, futon coverings, futon covers, blankets, blanket coverings, blanket covers, sheets, pillow batting, pillowcases, stuffed animal batting, disposable diapers, sanitary products, hygiene products, sewing thread, filters, bag filters, dust collection filters, air cleaners, water purification filters, gas separation membranes, belts, tablecloths, belt conveyor base fabrics, optical fibers, sound absorbing materials, and heat insulating materials, but the applications of the fiber (Y) are not limited to these.

[0053] Furthermore, when the fiber (Y) is made into a nonwoven fabric, it is suitable for applications such as down, masks, oil-absorbing fabrics, waterproof fabrics, futon batting, futon coverings, futon covers, blankets, blanket coverings, blanket covers, sheets, pillow batting, pillow covers, stuffed animal batting, nonwoven fabrics, disposable diapers, sanitary products, hygiene products, filters, bag filters, dust collection filters, air cleaners, water purification filters, gas separation membranes, battery separator films, sound absorbing materials, and heat insulating materials, but the applications of nonwoven fabrics obtained from the fiber (Y) are not limited to these. [Example]

[0054] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In some cases, the following polymerization was carried out multiple times to obtain the amounts of polymer and composition required for evaluation.

[0055] [Measurement conditions, etc.] The conditions for measuring each physical property are as follows:

[0056] [Intrinsic viscosity [η]] The intrinsic viscosity [η] of the various polymers and resin compositions obtained in the following Examples and Comparative Examples was measured at 135°C in decalin solvent. Hereinafter, the intrinsic viscosity of the ultra-high molecular weight polyethylene (A) will be referred to as "intrinsic viscosity [η] a Similarly, the intrinsic viscosity of polyethylene (B) is sometimes expressed as "Intrinsic viscosity [η] b " is sometimes written as ".

[0057] 〔density〕 The density of the polyethylene (B) was measured in accordance with ASTM D1505.

[0058] [Example 1] [Preparation of solid titanium catalyst component [C1]] 95.2 g of anhydrous magnesium chloride, 398.1 g of decane, and 306 g of 2-ethylhexyl alcohol were placed in a reaction vessel and heated at 140°C for 6 hours. After the solution in the reaction vessel was cooled to 50°C, 17.6 g of ethyl benzoate was added, and the mixture was stirred and mixed at 130°C for 1 hour to obtain a homogeneous solution. The homogeneous solution thus obtained was cooled to room temperature, and then 50 ml of the homogeneous solution was added dropwise over 60 minutes with stirring to 200 ml of titanium tetrachloride maintained at 0°C. After the addition, the resulting mixture was maintained at 0°C for 1 hour, then the temperature of the mixture was raised to 20°C over 1 hour, and then further raised to 80°C over 30 minutes. When the temperature of the mixture reached 78°C, 2.35 g of ethyl benzoate was added to the mixture, and the reaction was continued for 2 hours while maintaining the temperature at 80°C. After the 2-hour reaction, the solid was collected by hot filtration, resuspended in 200 ml of titanium tetrachloride, and then heated again at 90°C for 2 hours. After the second heating reaction, the solid was collected again by hot filtration, washed with 90°C decane until no free titanium compounds were detected in the washes, and then thoroughly washed with room-temperature hexane.

[0059] The solid titanium catalyst component prepared by the above procedure was stored as a decane slurry, and a portion of this was dried to examine the catalyst composition. The composition of the dried solid titanium catalyst component [C1] was 3.1 mass% titanium, 18 mass% magnesium, 60 mass% chlorine, 15.4 mass% ethyl benzoate, and 1.5 mass% 2-ethylhexyl alcohol residue.

[0060] [Production of polyethylene resin composition (X1)] A 1-liter polymerization vessel, thoroughly purged with nitrogen, was charged with 500 ml of purified decane at room temperature, and 0.5 mmol of triisobutylaluminum and a solid titanium catalyst component [C1] (0.01 mmol of titanium atom equivalent) were added at 80°C. Hydrogen was then fed until the pressure inside the polymerization vessel reached 0.406 MPaG (gauge pressure), followed by ethylene feeding until the pressure inside the polymerization vessel reached 0.66 MPaG (gauge pressure). First-stage ethylene polymerization was carried out at 85°C. The ethylene feed was stopped when 119 liters of ethylene had been fed, and the vessel was rapidly cooled to 45°C. The vessel was then depressurized and purged with nitrogen. By carrying out the first-stage ethylene polymerization under these conditions, polyethylene (B1) was obtained. Next, ethylene was fed into the polymerization reactor until the pressure inside the polymerization reactor reached 0.60 MPaG in gauge pressure, and second-stage ethylene polymerization was carried out at a temperature of 53°C. When 21 liters of ethylene had been fed, the ethylene feed was stopped, the temperature was rapidly cooled to 40°C, and then the pressure was released and purging was carried out. Note that by carrying out the second-stage ethylene polymerization under the above conditions, ultra-high molecular weight polyethylene (A1) can be obtained. The resulting slurry containing the solid was filtered and dried under reduced pressure overnight at a temperature of 80° C. The resulting ethylene resin composition (X1) weighed 190 g and had an intrinsic viscosity [η] in decalin solvent at 135° C. of 3.9 dl / g.

[0061] [Analysis of each component in polyethylene resin composition (X1)] Polyethylene (B1) content and properties Of the polymerizations carried out to produce polyethylene resin composition (X1), only the first stage polymerization was carried out separately under the same conditions as those used to produce polyethylene resin composition (X1). The yield of the resulting ethylene polymer was 162 g. Since polyethylene (B1) was produced by this polymerization, the content of polyethylene (B1) in polyethylene resin composition (X1) (yield 190 g) was calculated to be 85 mass %. The intrinsic viscosity [η] of the resulting polyethylene (B1) was measured in decalin solvent at 135°C and found to be 1.0 dl / g. The density of the resulting polyethylene (B1) was 971 kg / m 3 It was.

[0062] Ultra-high molecular weight polyethylene (A2) content and intrinsic viscosity [η] The first stage polymerization of the polymerization carried out to produce the polyethylene resin composition (X1) was omitted, and only the second stage polymerization was carried out separately under the same conditions as those used to produce the polyethylene resin composition (X1), thereby producing an ultra-high molecular weight polyethylene (A2). The ultra-high molecular weight polyethylene (A2) had an intrinsic viscosity [η] of 30 dL / g. Next, the molecular weight distribution of the ultra-high molecular weight polyethylene (A2) was measured by gel permeation chromatography (GPC). The results were compared with those of the polyethylene resin composition (X1) by GPC. The peak position and shape of the chromatogram were consistent with those of the high molecular weight component (ultra-high molecular weight polyethylene (A1)) contained in the polyethylene resin composition (X1). Based on this result, the physical properties of the ultra-high molecular weight polyethylene (A1) were considered to be the same as those of the ultra-high molecular weight polyethylene (A2). In other words, the intrinsic viscosity [η] of the ultra-high molecular weight polyethylene (A1) was determined to be 30 dL / g.

[0063] [Granulation of polyethylene resin composition (X1)] The obtained polyethylene resin composition (X1) was dry-blended with Irganox 1010 (manufactured by BASF), Irgafos 168 (manufactured by BASF), and calcium stearate (manufactured by NOF Corporation). The blend amounts of each substance were 0.1% by mass for Irganox 1010, 0.2% by mass for Irgafos 168, and 0.12% by mass for calcium stearate, assuming the composition after dry blending to be 100% by mass. The composition after dry blending was melt-kneaded using a twin-screw extruder (manufactured by Technovel, φ=15 mm, L / D=30, cylinder temperature: 200°C), and then granulated into pellets.

[0064] [Fiber manufacturing] Using the resulting polyethylene resin composition (X1) as a raw material, a Capilograph (manufactured by Toyo Seiki Seisaku-sho, Ltd.) was used to produce a raw yarn having a diameter of 0.98 mm at a temperature of 250°C and a nozzle diameter of 1.0 mm. The resin extrusion rate and take-up rate were adjusted so that the nozzle diameter and the diameter of the raw yarn were the same. Next, using a dry fiber drawing apparatus (furnace length: 1.0 m, feed bobbin diameter: 5.0 cm, take-up bobbin diameter: 5.0 cm), drawing was performed under the following conditions and at the draw ratio shown in Table 1 to obtain fiber (Y1). The draw ratio was calculated as the draw ratio after the first and second drawing. Primary stretching: Furnace temperature setting 125°C, feed speed 1 rpm, winding speed 12 rpm Secondary stretching: Furnace temperature setting 140°C, feed speed 1 rpm, winding speed 1.3 to 5.0 rpm

[0065] [Fiber evaluation] <Phase structure> The fiber (Y1) was cut using a microtome to prepare thin sections of the fiber. The fiber cross section was then observed using a laser microscope (Olympus) with a 1000x objective lens, and the homogeneity of the fiber was determined based on the following criteria. Homogeneous phase: No domains larger than 3 μm were observed in the cross section of the fiber. Sea-island structure: Domains larger than 3 μm were observed in the cross section of the fiber. The evaluation results of the obtained fiber (Y1) are shown in Table 1.

[0066] <Fiber diameter> The diameters of three arbitrary points on the fiber (Y1) were measured using a TRUSCO digital caliper (product number: TDN-100), and the average value was taken as the fiber diameter (D: denier). The fiber diameters of the obtained fiber (Y1) are shown in Table 1.

[0067] <Fiber tensile strength> The breaking strength (the strength of the force applied when the test fiber breaks) [gf] of the fiber (Y1) was measured using a tensile tester (manufactured by Instron). The test conditions were chuck distance: 210 mm, pulling speed: 50 mm / min, measurement environment temperature: 23°C, and standard conditions (a dry state where the fiber is not wet). The value obtained by dividing the breaking strength by the fiber diameter [D] of the fiber (Y1) was taken as the tensile strength. That is, the tensile strength was calculated using the following formula. The results are shown in Table 1. Tensile strength [gf / D] = Breaking strength [gf] / Fiber diameter [D]

[0068] [Example 2] The production of the resin composition, granulation of the resin composition, production of fibers, and evaluation of the fibers were carried out in the same manner as in Example 1, except that in the second-stage polymerization for producing the polyethylene resin composition (X1), the ethylene polymerization temperature was changed from 53°C to 80°C. The evaluation results of the obtained polyethylene resin composition (X2) and fiber (Y2) are shown in Table 1.

[0069] [Comparative Example 1] A polyethylene resin composition (cX1) was produced by interchanging the first-stage polymerization conditions and second-stage polymerization conditions of Example 1. Specifically, the catalyst component introduction temperature was changed from 80°C to 48°C, hydrogen was not fed in the first-stage polymerization, the ethylene polymerization temperature was changed from 85°C to 53°C, and the ethylene feed rate was changed from 119 liters to 21 liters. Furthermore, in the second-stage polymerization, hydrogen was fed until the pressure inside the polymerization vessel reached 0.40 MPaG in gauge pressure, the ethylene polymerization temperature was changed from 53°C to 85°C, and the ethylene feed rate was changed from 21 liters to 119 liters. The other conditions were the same as in Example 1 to produce a resin composition, and the resin composition was granulated, and fibers were produced and evaluated. The evaluation results of the obtained polyethylene resin composition (cX1) and fiber (cY1) are shown in Table 1.

[0070] Comparative Example 2 A resin composition was produced under the same conditions as in Comparative Example 1, except that the ethylene feed rate in the first-stage polymerization was changed from 21 liters to 33.6 liters and the ethylene feed rate in the second-stage polymerization was changed from 119 liters to 106.4 liters. The resin composition was then granulated, and fibers were produced and evaluated. The evaluation results of the obtained polyethylene resin composition (cX2) and fiber (cY2) are shown in Table 1.

[0071] [Table 1]

Claims

1. It comprises 5 to 40 parts by mass of an ultra-high molecular weight polyethylene (A) that satisfies the following requirement (a-1), and 95 to 60 parts by mass of a low-molecular weight or high-molecular weight polyethylene (B) that satisfies the following requirements (b-1) and (b-2) (the total amount of polyethylene (A) and polyethylene (B) being 100 parts by mass), Fiber (Y) having an intrinsic viscosity [η] measured in decalin solvent at 135 ° C. in the range of 1.5 to 15 dl / g and at least a part of which forms a homogeneous phase: (a-1) The intrinsic viscosity [η] measured in decalin solvent at 135°C is 8 to 50 dl / g; (b-1) The intrinsic viscosity [η] measured in decalin solvent at 135°C is 0.1 to 5 dl / g; (b-2) Density is 950 to 985 kg / m 3 is.

2. The fiber (Y) according to claim 1, wherein the homogeneous phase is a phase in which no domains of 3 μm or more are observed when the cross section of the fiber is observed with a laser microscope at a magnification of 1000 times.

3. The fiber (Y) according to claim 1, having a fiber diameter of 200 denier or less.

4. The fiber (Y) according to claim 1, wherein the draw ratio is 25 times or more.

5. The intrinsic viscosity [η] measured in decalin solvent at 135°C is 0.1 to 5 dl / g, and the density is 950 to 985 kg / m 3 a first step of producing a low- to high-molecular-weight polyethylene (B), a second step of producing, after the first step, an ultra-high molecular weight polyethylene (A) having an intrinsic viscosity [η] measured in a decalin solvent at 135°C in the range of 8 to 50 dl / g; by a multi-stage polymerization method including at least two steps of a production step of producing a polyethylene resin composition (X) having an intrinsic viscosity [η] measured in a decalin solvent at 135°C in the range of 1.5 to 15 dl / g and at least a part of which forms a homogeneous phase; a spinning step of spinning the polyethylene resin composition (X); A method for producing a fiber (Y), comprising:

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